Various technologies have been developed that provide navigation-related and map-related services. For example, vehicle navigation systems can determine where a vehicle is located and provide directions to travel to a desired destination. Also, Internet sites are available that provide maps, directions for traveling to a desired destination from a specified starting point, and other map-related services. Further, hand-held devices are available that can determine one's position and provide a map of one's surroundings.
In order to provide these and other map-related functions and features, navigation systems use geographic data. The geographic data may be in the form of one or more geographic databases that include data representing physical features in the geographic region. The geographic database includes information about the represented geographic features, such as one-way streets, position of the roads, speed limits along portions of roads, address ranges along the road portions, turn restrictions at intersections of roads, direction restrictions, such as one-way streets, and so on. Additionally, the geographic data may include points of interest, such as restaurants, hotels, airports, gas stations, stadiums, police stations, and so on.
This geographic data may be stored in a geographic database, such as a geographic database published by NAVTEQ North America, LLC of Chicago, Ill. In addition to the data obtained by a map vendor, content sources have data regarding locations in a geographic area. The content sources may provide their data to the map vendor for inclusion into the geographic database. For example, an owner of a chain restaurant may provide the map vendor with a current list of all their locations and for each of the locations the list may include address, telephone numbers, hours of operation, menu, web page address, and other information about the location.
As the amount of information stored in a geographic database increases, it becomes more difficult for the map vendor to add the third party data to the geographic database. As a result, location content management systems have been developed to allow multiple parties to provide data related to a location, which is sometimes referred to as “location content” or simply “content.” The location content management system provides a link between the location content and the geographic location associated with the content. The link is a location code that the location content management system assigns to a location.
A location code may be assigned to any location where a person can travel. For example, a person may want to travel to a particular office on a particular floor in a particular building in a geographic region. Using this example, the location content management system assigns a location code to each of the office, floor, and building. The location content management system may also assign a location code to stairs and/or an elevator if the floor is not on the ground level of the building. By assigning location codes in this manner, a navigation system can provide route guidance to a user for traveling to the office within the building.
While the location content management system provides a way for multiple parties to provide content regarding a location, there continues to be room for new features and improvements in the location content management system. One area for improvement is how to represent linear features in the location content management system. The location code references a point location minimally identified by latitude and longitude. However, in some situations it would be beneficial for a location code to reference a linear feature.
As a linear location code, like the point location code, necessarily remains outside a geographic database, the geographic database's two representations of linear objects, links and strands, are not suitable for representing linear features in the location content management system. A link is a geographic object with two nodes (a reference node and a non-reference node) and zero or more intermediate shape points. A strand is a directed sequence of links used by conditions defined in the geographic database. Links suffer from the problem of being split and merged due to attribution requirements, while strands suffer from the problem of being so tightly coupled to conditions that the strand can only be referenced by the condition. Thus, the linear location code needs to represent a linear feature in a manner that overcomes the problems associated with links and strands.